<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        let str = 'addddasfafdssadaf'
        let obj = {}

        for (let i = 0; i <= str.length; i++) {
            let chars = str.charAt(i)
            if (obj[chars]) {
                obj[chars]++
            } else {
                obj[chars] = 1
            }
        }
        console.log(obj);

        let max = 0
        let ch = ''
        for (const k in obj) {
            if (obj[k] > max) {
                max = obj[k]
                ch = k
            }
        }
        console.log('出现最多的字符', ch);
        console.log(max);
    </script>
</body>

</html>